Question

两者都选择产生数字。

但是，我似乎无法分开。

期望输出为~9％

代码：

select

(select count(b.booking_id) from booking b where b.pickup_date > '01 feb 2014' and b.pickup_date < '01 mar 2014')

/

(select count(q.quote_id) from quoting q where q.pickup_date > '01 feb 2014' and q.pickup_date < '01 mar 2014')

Answer 1

select CAST(A.X AS NUMERIC)/ CAST(NULLIF(B.Y, 0) AS NUMERIC)
FROM
(select count(b.booking_id) AS X 
from booking b 
where b.pickup_date > '01 feb 2014' 
and b.pickup_date < '01 mar 2014') A
,
(select count(q.quote_id) AS Y 
from quoting q 
where q.pickup_date > '01 feb 2014' 
and q.pickup_date < '01 mar 2014') B

你总是得到零的原因是

SELECT (50000 /550000)

两个传递的值都是INT，返回值也是INT，没有转换数据类型。

但是，如果你要做如下

SELECT CAST(50000 AS NUMERIC)/ CAST(550000 AS NUMERIC)

或者甚至

SELECT (50000 /550000.12121212)

您将获得正确的结果。原因是在First查询中，您正在显式转换为数据类型Numeric。

在第二个查询中，由于数据类型优先级，Sql Server会从INT到DECIMAL进行隐式转换。阅读此处以了解有关Data Type Precedence (Transact-SQL)

的更多信息

Answer 2

由于您正在使用整数，因此select正在进行整数运算。您需要将计数语句转换为双精度才能在2/4的情况发生时获得结果，并检查空值

PSEUDO CODE

SELECT CAST(A AS DECIMAL(13,5) / nullif(CAST (B AS DECIMAL(13,5), 0.0)

MSSQL 2008 - 我喜欢将一个选择除以另一个

2 个答案: